November 30th

Franklin’s Bumblebee: Already Too Late? – by Matt Stanfield

Humans are inquisitive and acquisitive, predisposed to hanker after novelty. Throughout history, the rare and obscure have enticed us. Those insect species associated with multitudinous swarms struggle to appeal to this psychological trait of ours. If they do get our attention, it is generally for other reasons.

Bees, for instance, have recently been making news for their precipitous declines. The anxious coverage of this phenomenon is very much linked to immediate human concerns. It is estimated that one-third of our kind’s food is pollination-dependent. Thus the conservation of bees is widely seen as of direct interest to our own species, in a way that the conservation of many other organisms is not. Even if the motive is a self-interested one, humans would do well to work on arresting and reversing bee declines, given we are far from the only species in need of their continued presence on the planet.

Though bees are often considered only en masse, as a homogenous force, this piece will look at just one bee species: Franklin’s bumblebee (Bombus franklini). This insect has not been seen alive since 2006 and may already be extinct. Absent any further confirmed sightings, it will likely be some time before Franklin’s bumblebee is declared gone forever. This is quite standard, as far larger and more conspicuous species have occasionally been known to vanish from record for decades or more. Still, for this small creature the signs are not promising.

B. franklini has had a highly restricted range ever since it was first described in 1922, possibly the smallest of any bumblebee on Earth. So far as we know, they only ever lived within a limited tract from southern Oregon to northern California. Specifically, these bees were found in the Klamath Mountains, an extremely picturesque area incorporating a substantial amount of officially protected land.

Between 1998 and 2006, the bees’ home range was examined thoroughly by Dr Robbin W. Thorp. Thorp’s initial findings showed that Franklin’s bumblebee was slightly more widespread than previously assumed. Each year, his surveys included at least five potential new sites where the bees might exist. Up to the year 2000, Franklin’s bumblebee was indeed found at seven of these new sites.

From 2001 onwards, no new locations yielded any B. franklini sightings. Worse, the insects started disappearing from areas which they had previously occupied. The 2004 and 2005 surveys failed to turn up a single Franklin’s bumblebee anywhere within their known range. In 2006, the situation differed, inasmuch as precisely one member of the species was seen during an entire year’s searching. Without Dr Thorp’s work, the fading of this insect might never have been noticed at all.

It is fitting that B. franklini vanished before our eyes so near the western edge of North America, where the ever-shifting frontier of colonial mythology finally came up against the Pacific and an insurmountable obstacle to further expansion. In the end, nothing is inexhaustible, whether it be the “Wild West” or the Earth’s legions of invertebrates.

A female Franklin’s bumblebee. Image public domain

So, whatever happened to Franklin’s bumblebee over the first few years of the new millennium?

The IUCN identifies two main agents of the species’ possible demise. First, it notes that our species’ commercial interest in bumblebees may imperil them. Commercial usage of bumblebee colonies to pollinate crops both indoors and out has brought wild populations into contact with new pathogens. In recent decades, bumblebees have become commercialised, with colonies transported across nations. Tracheal mites, intestinal protozoa and others have travelled far and wide with these bees.

Even where pathogens do not kill bumblebees directly, the sophisticated nature of bee behaviour renders it easily disrupted. The capacity of bumblebees to learn to handle or feed on newly-encountered flower types may be reduced by infection. In turn, this shrinks the amount of food which forager bees bring into the colony, diminishing its size and ability to produce offspring. Thus, the colony may collapse entirely.

The second culprit which the IUCN puts forward in the case of the vanished B. franklini is agricultural intensification, most importantly regarding pesticide usage. Pesticides can prove immediately deadly to bumblebees, or eat away at the health of their colonies as foragers unwittingly bring poisonous chemicals into their homes.

Recently, a class of pesticides known as neonicotinoids has been identified as especially dangerous to bees, a discovery picked up on by some sections of the media. Whether such attention might dissuade humanity from gambling with the future of a crucial pollinator genus is yet to be seen.